Tube pump

ABSTRACT

A tube pump capable that prevents and minimizes torque variation in a drive motor regardless of the rotation direction of a rotor unit includes a casing in which a liquid-flowing tube is arranged; a drive motor provided with a driving shaft rotatable in forward and reverse directions; a rotor body; roller holders supported on the rotor body to swing with respect to the rotor body; pressing rollers rotatably supported on the roller holders to press the tube against an inner circumferential wall surface of the casing; and biasing units biasing the roller holders, when swung, to be returned to a pre-swing position. The roller holders are configured to swing with respect to the rotor body in a direction opposite to a rotation direction of the rotor body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tube pump mounted to a dialysis device or the like.

2. Description of the Related Art

A tube pump that discharges a liquid existing within a liquid-flowing tube by rotating a rotor unit having pressing rollers with a drive motor and squeezing the tube with the pressing rollers is known in the art. Such a tube pump is disclosed in, e.g., Japanese Patent Application Publication No. H06-218042. In this tube pump, the rotor unit includes a rotor body engaging with a driving shaft of the drive motor, a pair of swing arms swingably pivoted to the rotor body in a symmetrical relationship with each other, pressing rollers rotatably supported on the tip end portions of the swing arms and compression springs arranged to bias the swing arms in an outwardly opening direction. The rotor body and the swing arms being made essentially of a metallic material such as aluminum die-cast or the like.

It is sometimes the case that, during retransfusion or depending on the specifications of a dialysis device, the tube pump is used by reversely rotating the rotor unit. In this case, it is desirable to ensure that the drive motor does not suffer from severe torque variation.

The swing arms of the tube pump disclosed in Japanese Patent Application Publication No. H06-218042 are configured to apply a specified pressing force to the tube by bringing the pressing rollers into contact with the tube at a predetermined angle during forward rotation of the rotor unit. Because of this arrangement, the pressing rollers cannot make contact with the tube at the same predetermined angle during reverse rotation of the rotor unit, which results in an increase in the pressing force applied to the tube by the pressing rollers. As a consequence, the reaction force (load) of the tube acting against the pressing rollers (rotors) will be increased and severe torque variation will occur in the drive motor (or the driving shaft). Accordingly, a demand has existed for a tube pump capable of suppressing torque variation in the drive motor regardless of the rotation direction of the rotor unit.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide a tube pump that prevents and minimizes torque variation in a drive motor regardless of the rotation direction of a rotor unit.

In accordance with a first preferred embodiment of the present invention, a tube pump preferably includes a casing including an arc-shaped inner circumferential wall surface along which a liquid-flowing tube is arranged; a drive motor provided with a driving shaft rotatable in forward and reverse directions; a rotor body arranged in a center position of the arc-shaped inner circumferential wall surface to rotate together with the driving shaft; roller holders supported on the rotor body to swing with respect to the rotor body and arranged to move toward and away from the driving shaft on a plane that is perpendicular or substantially perpendicular to the driving shaft; pressing rollers rotatably supported on the roller holders and arranged to press the tube against the inner circumferential wall surface; and biasing units interposed between the rotor body and the roller holders to bias the roller holders away from the driving shaft and to bias the roller holders, when swung, to be returned to a pre-swing position, the roller holders configured to swing with respect to the rotor body in a direction opposite to a rotation direction of the rotor body.

With such a configuration, if the rotor body is rotated by the rotation of the driving shaft, the pressing roller pressing the tube receives a reaction force (load) from the tube. The load acts on the roller holder supporting the pressing roller. If the load is equal to or greater than a predetermined value, the roller holder swings with respect to the rotor body in a direction opposite to the rotation direction of the rotor body. This prevents a large load from being applied to the rotor body through the roller holder, thereby preventing an occurrence of a large torque variation in the driving shaft. In particular, even when the rotor body is rotated in the reverse direction, it is possible to drive the drive motor with no large torque burden borne by the drive motor as compared with the forward rotation direction.

If the rotor body further rotates and if the pressing roller pressing the tube becomes detached from the tube and fails to receive the load from the tube, the roller holder that is swung with respect to the rotor body is returned to the pre-swing position by the biasing force of the biasing units. As the rotor body rotates in this manner, the tube is squeezed by the pressing rollers to discharge the liquid existing therein.

In accordance with a second preferred embodiment of the present invention, a tube pump is provided in which the rotor body includes a pair of engagement projection portions extending in an extension direction of the driving shaft, the engagement projection portions arranged in opposite side areas of the rotor body along a direction that is perpendicular or substantially perpendicular to the extension direction of the driving shaft and the biasing direction of the biasing units, the roller holders including a pair of engagement recess portions extending in the extension direction of the driving shaft and arranged to engage with the engagement projection portions to thereby provide rotation fulcrums for the roller holders.

With such a configuration, if the rotor body is rotated by the rotation of the driving shaft, the rotation of the rotor body is transferred to the roller holder engaging with the rotor body. The leading engagement projection portion of the roller holder comes into engagement with the leading engagement recess portion of the roller holder. The rotor body pulls the roller holder in the rotation direction. Thus, due to the reaction force of the tube acting on the pressing roller, a swing force acts on the roller holder about a rotation fulcrum, i.e., the leading engagement recess portion and the leading engagement projection portion engaging with each other. The roller holder is swung against the pressing force to release the load. This prevents a large load from being applied to the rotor body through the roller holder, thereby preventing the occurrence of large torque variation in the driving shaft.

If the rotor body further rotates and if the pressing roller pressing the tube becomes detached from the tube and fails to receive the load from the tube, the roller holder swung with respect to the rotor body is returned to the pre-swing position by a biasing force provided by the biasing units. By such rotation of the rotor body, the other pressing roller kept out of contact with the tube operates just like the pressing roller which has pressed the tube. As the rotor body rotates in this manner, the tube is continuously squeezed by the pressing rollers to discharge the liquid contained therein.

Since the rotor body and the roller holders are brought into engagement with each other by the engagement projection portions and the engagement recess portions to define the rotation fulcrums, the roller holders can swing with respect to the rotor body with a simplified configuration.

If the rotor body is rotated in the reverse direction the leading engagement projection portion of the roller holder (positioned opposite to the engagement projection portion mentioned above) comes into engagement with the leading engagement recess portion of the roller holder (positioned opposite to the engagement recess portion mentioned above). Thus, the roller holder swings about a rotation fulcrum, i.e., the engagement position noted above. In other words, the roller holder swings against the biasing force to release the load acting on the pressing roller. This provides a structure in which, depending on the rotation direction of the driving shaft, the rotation fulcrum of the roller holder in the rotor body is changed to a position where the load of the tube is easily released. Accordingly, even when the rotor body is rotated in the reverse direction, it is possible to drive the drive motor with no large disparity in torque burden borne by the drive motor as compared with the forward rotation.

The above and other elements, features, steps, characteristics and advantages of the preferred embodiments of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the overall configuration of a tube pump according to a first preferred embodiment of the present invention.

FIG. 2 is a perspective view of a rotor unit of the tube pump shown in FIG. 1.

FIG. 3 is a section view of the rotor unit taken along line III-III in FIG. 2.

FIG. 4 is a section view of the rotor unit taken along line IV-IV in FIG. 2.

FIG. 5 is a partial section view illustrating the operating state of the rotor unit during counterclockwise rotation thereof in the tube pump shown in FIG. 1.

FIG. 6 is a partial section view illustrating the operating state of the rotor unit during clockwise rotation thereof in the tube pump shown in FIG. 1.

FIG. 7 is a perspective view showing a rotor unit of a tube pump according to a second preferred embodiment of the present invention.

FIG. 8 is a section view of the rotor unit taken along line VIII-VIII in FIG. 7.

FIG. 9 is a section view of the rotor unit taken along line IX-IX in FIG. 7.

FIG. 10 is a perspective view showing a rotor unit of a tube pump according to a third preferred embodiment of the present invention.

FIG. 11 is a section view of the rotor unit taken along line XI-XI in FIG. 10.

FIG. 12 is a section view of the rotor unit taken along line XII-XII in FIG. 10.

FIG. 13 is a plan view illustrating the operating state of the rotor unit in the tube pump shown in FIG. 10.

FIG. 14 is a perspective view showing a rotor unit of a tube pump according to a fourth preferred embodiment of the present invention.

FIG. 15 is a section view of the rotor unit taken along line XV-XV in FIG. 14.

FIG. 16 is a section view of the rotor unit taken along line XVI-XVI in FIG. 14.

FIG. 17 is a plan view illustrating the operating state of the rotor unit in the tube pump shown in FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Preferred Embodiment

A tube pump 1 according to a first preferred embodiment of the present invention will now be described with reference to FIGS. 1 through 4.

First, the overall configuration of the tube pump 1 will be described with reference to FIG. 1. The tube pump 1 preferably includes a casing 2 within which a liquid-flowing tube (see FIG. 5) is arranged, a drive motor 4 including a driving shaft 4 a, a rotor unit 5 arranged within the casing 2 and configured to squeeze the tube 3 due to the rotation of the driving shaft 4 a, and a cover unit 6.

The casing 2 is preferably made of, e.g., a synthetic resin, and preferably includes an inner circumferential wall surface 2 a, a reception void portion 7, a cover 8, guide recess portions 9 and tube clamps 10. The inner circumferential wall surface 2 a preferably has an arc shape when the casing 2 is viewed in the extending direction of the driving shaft 4 a (see FIG. 5). The reception void portion 7 is opened at the upper side thereof to accommodate the tube 3 and the rotor unit 5. The inner circumferential wall surface 2 a partially defines the reception void portion 7. The cover 8 is preferably made of, for example, a transparent resin and is arranged to open and close the upper surface of the reception void portion 7. The guide recess portions 9 are opened in the horizontal direction and serve to guide the tube 3 toward the outside of the reception void portion 7. The tube clamps 10 press the tube 3 arranged in the guide recess portions 9 and lock the tube 3 in a removable manner. The casing 2 may also be made of, for example, a metal instead of a resin, if so desired.

The tube 3 is preferably made of, for example, a transparent resin with a predetermined elasticity. The tube 3 is arranged along the inner circumferential wall surface 2 a within the reception void portion 7. The driving shaft 4 a of the drive motor 4 is rotatable in both the forward and reverse directions. The driving shaft 4 a is arranged at the center of an arc defining the inner circumferential wall surface 2 a.

The cover unit 6 preferably includes a rotor cover portion 6 a connected to the rotor unit 5 and configured to cover the outer surface of the rotor unit 5 and a handle portion 6 b which can be folded into the cover portion 6 a and can be unfolded and gripped by a hand. The handle portion 6 b is arranged to be used to manually rotate the rotor unit 5 in such an instance where the drive motor 4 is not operated due to, for example, failure or other causes. In the following description, the cover unit 6 is depicted as being detached from the rotor unit 5 for the sake of convenience in description.

Next, details of the rotor unit 5 will be described with reference to FIGS. 2 to 4. As shown in FIG. 2, the rotor unit 5 preferably includes a rotor body 20, a pair of roller holders 40 engaging with the rotor body 20, a pair of pressing rollers 50 rotatably supported on the roller holders 40 and compression coil springs (biasing units) 60 having a specified predetermined resiliency. The rotor body 20 is a member that rotates together with the driving shaft 4 a about the center of the arc defining the inner circumferential wall surface 2 a of the casing 2. As shown in FIG. 2, the rotor body 20 preferably includes a top plate portion 21, a bottom plate portion 22, a connecting portion 23, a shaft hole portion 24, four engagement projection portions 25 preferably arranged to have a symmetrical relationship with respect to the driving shaft 4 a, and spring-receiving recess portions 28.

The top plate portion 21 preferably has a substantially rectangular shape when seen in a plan view, for example, and makes up the upper portion of the rotor body 20. As shown in FIGS. 2 and 3, the bottom plate portion 22 preferably has a substantially rectangular shape when seen in a plan view, for example, and makes up the lower portion of the rotor body 20. The top plate portion 21 and the bottom plate portion 22 are arranged in a parallel or substantially parallel relationship with each other. The top plate portion 21 and the bottom plate portion 22 are perpendicular or substantially perpendicular to the driving shaft 4 a. The connecting portion 23 is arranged between the top plate portion 21 and the bottom plate portion 22 to interconnect the top plate portion 21 and the bottom plate portion 22. As can be seen in FIGS. 3 and 4, the connecting portion 23 preferably includes a centrally-located polygonal pillar portion 23 a and partition wall portions 23 b. The polygonal pillar portion 23 a extends in the extension direction of the driving shaft 4 a and has a substantially rectangular columnar shape, for example. As can be noted in FIG. 3, the partition wall portions 23 b extend from the centers of the opposite side surfaces of the polygonal pillar portion 23 a in the direction P4 (or P5) intersecting the biasing direction P2 (or P3) of the compression coil springs 60 (hereinafter referred to as “biasing direction”).

As shown in FIGS. 2 through 4, the shaft hole portion is arranged to pass through the top plate portion 21, the connecting portion 23 and the bottom plate portion 22. The shaft hole portion 24 has a reduced diameter portion arranged above the connecting portion 23. The driving shaft 4 a is inserted into the shaft hole portion 24 from below the rotor body 20 to the reduced diameter portion. A screw is preferably fastened to the driving shaft 4 a from above the rotor body 20, thereby fixing the rotor body 20 to the driving shaft 4 a. Though not explicitly depicted, the rotor cover portion 6 a is simultaneously fixed onto the rotor body 20 by the screw arranged to fasten the driving shaft 4 a. The top plate portion 21, the connecting portion 23 and the bottom plate portion 22 are preferably provided as a single piece by, e.g., a GF-reinforced engineering plastic filled with glass fibers. The rotor body 20 thus configured is connected to the driving shaft 4 a.

In the rotor body 20, the engagement projection portions 25 are provided in four corner positions lying on a substantially square line about the driving shaft 4 a. The engagement projection portions 25 extend in the extension direction P1 of the driving shaft 4 a. The engagement projection portions 25 are arranged to protrude in the direction P4 (or P5) intersecting the biasing direction P2 (or P3) of the compression coil springs 60 and the extension direction P1 of the driving shaft 4 a. More specifically, each of the engagement projection portions 25 preferably includes a shaft portion 26 fixed to the rotor body 20 (the top plate portion 21 and the bottom plate portion 22) and a collar portion 27 covering the circumferential surface of the shaft portion 26. The shaft portion 26 is preferably made from, for example, a metal material to have a cylindrical columnar shape. The collar portion 27 is preferably made from, for example, a resin material to have a cylindrical shape. The collar portion 27 is preferably made of, e.g., polyacetal having superior slidability. The engagement projection portions 25 thus configured engage with the roller holders 40. The spring-receiving recess portions 28 are arranged in the connecting portion 23 to extend toward the driving shaft 4 a and are configured to accommodate the compression coil springs 60.

The roller holders 40 are members arranged to rotatably support the pressing rollers 50. As shown in FIG. 3, the roller holders 40 are configured to have a substantially C-shaped cross-section opened toward the rotor body 20. The open-side opposite tip end sections of each of the roller holders 40 extend to go around to the positions where they are opposed to the surfaces of the engagement projection portions 25 facing in the biasing direction P3 (or P2). Each of the open-side opposite tip end sections defines an engagement recess portion 42. Each of the roller holders 40 preferably includes a roller reception portion 43 and a tube guide roller 47, both of which are arranged at the opposite side from the rotor body 20.

As shown in FIG. 3, the engagement recess portion 42 extends in the extension direction P1 of the driving shaft 4 a. The engagement recess portion 42 engages with the collar portion of the rotor body 20 (each of the engagement projection portions 25). The dimension of the engagement recess portion 42 in the biasing direction P2 (or P3) is greater than the dimension (diameter) of the collar portion 27. The surface of the engagement recess portion 42 making engagement (contacting) with the collar portion 27 preferably has an arc shape. The roller reception portion 43 preferably has a dented shape in the central area of the opposite surface of each of the roller holders 40 from the rotor body 20 with a specified gap left between the roller reception portion 43 and the outer circumferential surface of each of the pressing rollers 50. The tube guide roller 47 is provided adjacent to each of the pressing rollers 50. The tube guide roller 47 serves to restrict the position of the tube 3 in the extension direction P1 of the driving shaft 4 a.

As shown in FIGS. 2 and 3, the roller holders 40 configured as above are brought into engagement with the rotor body 20 in such a manner as to move toward or away from the driving shaft 4 a on the plane perpendicular or substantially perpendicular to the driving shaft 4 a. The engagement recess portions 42 of the roller holders 40 engage with the engagement projection portions 25 of the rotor body 20 in a rotatable (swingable) manner. As stated above, the open-side opposite tip end sections of each of the roller holders 40 extend around to the surfaces of the engagement projection portions 25 facing in the biasing direction P3 (or P2). Therefore, the roller holders 40 are not detached from the engagement projection portions 25 of the rotor body 20 even if they are swung as mentioned above. In this regard, each of the roller holders 40 engages with two of the engagement projection portions 25 and swings about the engagement projection portions 25. Thus, the roller holders 40 are supported on the rotor body 20 so as to swing with respect to the rotor body 20.

The pressing rollers 50 are rotatably supported on the roller holders 40 to press the tube 3 against the inner circumferential wall surface 2 a of the casing 2 (see FIG. 5). As shown in FIG. 4, each of the pressing rollers 50 preferably includes a support shaft 51, bearings 52 and a roller portion 53. The support shaft 51 extends parallel or substantially parallel to the extension direction P1 of the driving shaft 4 a and is fixed to each of the roller holders 40. The bearings 52 are fixed to the roller portion 53 and make sliding contact with the support shaft 51 to rotatably support the roller portion 53. The roller portion 53 is a portion that comes into contact with the tube 3 (see FIG. 5) and presses the tube 3.

As shown in FIGS. 3 and 4, the compression coil springs 60 are accommodated within the spring-receiving recess portions 28 of the rotor body 20 and are arranged between the rotor body 20 and the roller holders 40. One end of each of the compression coil springs 60 protrudes from each of the spring-receiving recess portions 28 and presses one of the roller holders 40. Consequently, the compression coil springs 60 bias the roller holders 40 (the pressing rollers 50) away from the driving shaft 4 a. Moreover, the compression coil springs 60 bias the roller holders 40 so that the roller holders 40 swung about the engagement projection portions 25 can be returned to the pre-swing position.

Next, the operation of the tube pump 1 according to the first preferred embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 is a partial section view illustrating the operating state of the rotor unit 5 during counterclockwise rotation thereof. FIG. 6 is a partial section view illustrating the operating state of the rotor unit during clockwise rotation thereof.

One of the pressing rollers 50 biased by the compression coil springs 60, i.e., the pressing roller 50 making contact with the tube 3 (the pressing roller 50 positioned at the upper side in FIG. 5), receives from the tube 3 a center-direction reaction force (load) acting toward the driving shaft 4 a. If the rotor body 20 is rotated counterclockwise in a plan view by the driving shaft 4 a as illustrated in FIG. 5, the pressing roller 50 making contact with the tube 3 receives not only the reaction force (load) applied by the tube 3 but also a reaction force (load) acting in the direction opposite to the rotation direction of the rotor body 20. Therefore, a resultant load amounting to the sum of the two reaction forces acts against the pressing roller 50.

In order to release the load, the roller holder 40 applied with the load swings (or is tilted) about a fulcrum, i.e., the loading one of the engagement projection portions 25 engaging with the roller holder 40. This reduces the load borne by the roller holder 40, thereby preventing the load from acting on the rotor body 20 through the roller holder 40. As a result, it is possible to prevent the load from acting on the driving shaft 4 a.

If the rotor body 20 further rotates and if the pressing roller 50 pressing the tube 3 becomes detached from the tube 3 and fails to receive the load from the tube 3, the roller holder 40 swung about the engagement projection portion 25 is returned to the pre-swing position by the biasing force (restoring force) of the compression coil spring 60. By such rotation of the rotor body 20, the other pressing roller 50 kept out of contact with the tube 3 (the pressing roller 50 positioned at the lower side in FIG. 5) comes into contact with the tube 3 and operates just like the pressing roller 50 positioned at the upper side in FIG. 5. As the rotor body 20 rotates in this manner, the tube 3 is continuously squeezed by the pressing rollers 50 to discharge the liquid provided therein.

On the other hand, if the rotor body 20 is rotated clockwise as illustrated in FIG. 6, the same operation as stated above occurs except that the roller holders 40 swing in the direction opposite to the afore-mentioned direction. Accordingly, even when the rotor body 20 is rotated clockwise, it is possible to drive the drive motor 4 without any burden of large torque, as in the case in the counterclockwise rotation.

The tube pump 1 of the first preferred embodiment described above provides the following effects. The tube pump 1 preferably includes the roller holders 40 capable of moving toward or away from the driving shaft 4 a on the plane perpendicular or substantially perpendicular to the driving shaft 4 a and supported to swing with respect to the rotor body 20; the pressing rollers 50; and the compression coil springs 60 arranged to bias the roller holders 40 away from the driving shaft 4 a while biasing the roller holders 40 to return back to the pre-swing position. The swing direction of the roller holders 40 with respect to the rotor body 20 is opposite to the rotation direction of the rotor body 20.

As a result of these unique features, if the pressing rollers 50 (the roller holders 40) receive an excessive reaction force (load) from the tube 3 by the rotation of the rotor body 20, the roller holders 40 can swing about the engagement projection portions 25 of the rotor body 20 to release the load. Accordingly, it is possible to prevent an excessive load from being applied to the rotor body 20 through the roller holders 40, consequently preventing torque variation in the driving shaft 4 a. In particular, even when the rotor body 20 is rotated in the reverse direction, it is possible to drive the drive motor 4 without the occurrence of large torque variation, as in the case in the forward rotation.

In the tube pump 1 described above, each of the rotor body 20 and the roller holders 40 is preferably molded as a single piece by a specified engineering plastic, for example. Accordingly, as compared with aluminum die-cast molding, it is possible to omit a hole-forming process and a finishing process otherwise performed after the molding process. It is also possible to omit after-processes such as a short-blast process and a plating process. Since the engineering plastic is smaller in specific gravity than a metal material and is superior in specific strength to a typical plastic material, it is possible to realize weight reduction of a tube pump.

In the tube pump 1 described above, the rotor body 20 includes the engagement projection portions 25 protruding in the specified direction and engaging with the roller holders 40. Each of the engagement projection portions 25 includes the metal-made shaft portion 26 fixed to the rotor body 20 and the resin-made collar portion 27 covering the shaft portion 26. Each of the roller holders 40 includes the engagement recess portion 42 extending in the extension direction of the driving shaft 4 a and engaging with the collar portion 27.

This enables the rotor body 20 and the roller holders 40 to engage with each other through the engagement projection portions 25 and the engagement recess portions 42. Use of the metal-made shaft portion 26 helps increase the strength of the engagement projection portions 25. Use of the resin-made collar portion 27 enables the engagement projection portions 25 to smoothly engage with the engagement recess portions 42. Thanks to this simplified configuration, the roller holders 40 can smoothly swing with respect to the rotor body 20. This makes it possible to minimize and prevent wear of the engagement projection portions 25 and the engagement recess portions 42. While the collar portion 27 of each of the engagement projection portions 25 is preferably provided by a cylindrical body slidably supported on the shaft portion 26 in the preferred embodiment described above, the present invention is not limited thereto. As an alternative example, the collar portion 27 may be provided by a (metal-made) outer race of a rolling bearing supported on the shaft portion 26.

In the tube pump 1 described above, the biasing units are preferably made up of the compression coil springs 60. The rotor body 20 is provided with the spring-receiving recess portions 28 to accommodate the compression coil springs 60. Use of the compression coil springs 60, which are general-purpose elements, makes it possible to provide the biasing units in an easy and cost-effective manner. Provision of the spring-receiving recess portions 28 makes it possible to easily secure the spaces for arrangement of the compression coil springs 60 and to shorten the length of the rotor body 20 in the biasing direction P2 (or P3).

Next, description will be made of other preferred embodiments of the present invention. With regard to other preferred embodiments, description will be centered on the points differing from the first preferred embodiment. The same components as those of the first preferred embodiment will be designated by like reference symbols but will not be described in detail. As for the points not specifically described in other preferred embodiments, the description on the first preferred embodiment is appropriately applied and/or incorporated by reference.

Second Preferred Embodiment

A tube pump 1A according to a second preferred embodiment of the present invention will be described with reference to FIGS. 7 through 9. FIG. 7 is a perspective view showing a rotor unit 5A of a tube pump 1A according to a second preferred embodiment of the present invention. FIG. 8 is a section view of the rotor unit 5A taken along line VII-VII in FIG. 7. FIG. 9 is a section view of the rotor unit 5A taken along line IX-IX in FIG. 7.

As shown in FIGS. 7 through 9, the tube pump 1A according to the second preferred embodiment differs from the tube pump 1 of the first preferred embodiment in terms of the configuration of the rotor body 20A of the rotor unit 5A. More specifically, major differences lie in that the rotor body 20A does not include the top plate portion 21 (see FIG. 2) and in that the engagement projection portions 25A and the connecting portion 23 are preferably provided as a single piece, for example.

Referring to FIGS. 7 and 8, the engagement projection portions 25A extend and protrude in the same directions as the extension direction and the protruding direction of the engagement projection portions 25 of the tube pump 1 according to the first preferred embodiment. The engagement projection portions 25A and the rotor body 20A (the connecting portion 23) are preferably defined by a single piece, for example. In other words, the engagement projection portions 25A are provided by a single monolithic piece with the connecting portion 23 and the bottom plate portion 22. Thus, the engagement recess portions 42 engage with the engagement projection portions 25A in a slidable manner. Other configurations and basic operations of the tube pump 1A of the second preferred embodiment remain the same as those of the tube pump 1 of the first preferred embodiment. No repeated description will be given in that regard.

The tube pump 1A of the second preferred embodiment described above provides the same effects as those of the first preferred embodiment and additionally provides the following effects. In the tube pump 1A of the second preferred embodiment, the rotor body 20A includes the engagement projection portions 25A preferably defined by a single piece with the rotor body 20.

While each of the rotor body 20 and the roller holders 40 is preferably defined by a single piece of engineering plastic in the first and second preferred embodiments, the present invention is not limited thereto. For example, only the rotor body 20 may be defined by a single piece by an engineering plastic, for example. The rotor body 20 and the roller holders 40 or the rotor body 20 may alternatively be defined by a single piece by a resin other than an engineering plastic, as far as the resin complies with the prescribed requirements on heat resistance, strength and flexural modulus, for example.

In addition, while two pressing rollers 50 are preferably provided in the rotor unit 5 or 5A along the biasing direction P2 (or P3) in the first and second preferred embodiments, the present invention is not limited thereto. For example, three or more pressing rollers 50 may be provided in the rotor unit 5 or 5A. The number of the tube guide rollers 47 may be increased if such a need arises.

Third Preferred Embodiment

Next, a tube pump 1B according to a third preferred embodiment of the present invention will be described with reference to FIGS. 10 through 12. FIG. 10 is a perspective view showing a rotor unit 5B of a tube pump 1B according to a third preferred embodiment of the present invention. FIG. 11 is a section view of the rotor unit 5B taken along line XI-XI in FIG. 10. FIG. 12 is a section view of the rotor unit 5B taken along line XII-XII in FIG. 10.

The biasing unit for biasing the roller holders is defined by a leaf spring 70 (see FIGS. 10 through 12) in the tube pump 1B of the third preferred embodiment, while the biasing units are preferably defined by the compression coil springs 60 (see FIG. 3) in the tube pump 1 of the first preferred embodiment. In this respect, the tube pump 1B of the third preferred embodiment differs largely from the tube pump 1 of the first preferred embodiment.

The tube pump 1B of the third preferred embodiment preferably includes a casing 2, a tube 3 and a rotor unit 5B arranged to squeeze the tube 3 upon rotation of a driving shaft 4 a (see FIG. 13). The rotor unit 5B preferably includes a rotor body 20B, a pair of roller holders 40B engaging with the rotor body 20B, a pair of pressing rollers 50 rotatably supported on the roller holders 40B, a leaf spring (biasing unit) 70 having a specified predetermined resilience, first bolts 73, first backing plates 74, first nuts 75, reception groove portions 77, second bolts 78, second backing plates 79, second nuts 80 and stopper portions 82.

The rotor body 20B is preferably made of a specified resin (e.g., an engineering plastic), for example. As shown in FIGS. 10 to 12, the rotor body 20B has a substantially polygonal pillar shape. A plurality of through-holes (not shown) extending in the direction perpendicular or substantially perpendicular to the extension direction P1 of the driving shaft 4 a is defined in specified portions of the rotor body 20B. The first bolts 73 are inserted into the through-holes. The reception groove portions 77 and the stopper portions 82 are provided in the rotor body 20B. The reception groove portions 77 and the stopper portions 82 will be described later.

As shown in FIG. 12, the cross section of each of the roller holders 40B taken along the axial direction of the support shaft 51 has a substantially square bracket shape. A plurality of through-holes (not shown) into which the second bolts 78 are inserted is provided in the portions of the roller holders 40B adjoining to the rotor body 20B.

As shown in FIGS. 10 through 12, the leaf spring 70 preferably includes a pair of transverse plate portions 71 extending substantially parallel to each other and a pair of longitudinal plate portions 72 extending in the direction perpendicular or substantially perpendicular to the transverse plate portions 71 and interconnecting the opposite ends of the transverse plate portions 72. Thus, the leaf spring 70 is configured to have a substantially polygonal sleeve shape. More specifically, as shown in FIG. 11, the leaf spring 70 is preferably provided into a substantially polygonal sleeve shape by two leaf springs each having a cross section of substantially square bracket shape taken along the direction perpendicular or substantially perpendicular to the driving shaft 4 a. In other words, the longitudinal plate portions 72 of the leaf spring 70 are divided in the positions corresponding to the centers of the roller holders 40B so that the terminal edges thereof can face toward each other. The longitudinal plate portions 72 thus divided are connected to the opposite ends of the transverse plate portions 71 to thereby define a square bracket shape. A plurality of through-holes (not shown) into which the first bolts 73 and the second bolts 78 are inserted is defined in specified portions of the leaf spring 70. The leaf spring 70 thus configured is arranged to cover the side surfaces of the rotor body 20B as shown in FIGS. 10 and 11.

The first bolts 73, the first backing plates 74 and the first nuts 75 are members arranged to fix the transverse plate portions 71 of the leaf spring 70 to the rotor body 20B. Each of the first backing plates 74 is preferably provided by a metal plate having a cross section of, e.g., substantially square bracket shape, and is provided with through-holes (not shown) arranged to permit insertion of the first bolts 73. The first bolts 73 are inserted into the through-holes of the first backing plates 74 and the through-holes of the rotor body 20B and are threadedly coupled with the first nuts 75.

The first nuts 75 are preferably provided by, e.g., rectangular metal plates, and are provided with female threads threadedly coupled with the first bolts 73. The first nuts 75 are accommodated within the reception groove portions 77. Use of the first bolts 73, the first backing plates 74 and the first nuts 75 makes it possible to firmly fix the transverse plate portions 71 to the rotor body 20B with the surface pressures of the first backing plates 74 and the first nuts 75.

The second bolts 78, the second backing plates 79, and the second nuts 80 are members arranged to fix the longitudinal plate portions 72 of the leaf spring 70 to the roller holders 40B as shown in FIGS. 10 through 12 and are members arranged to fix together the joints of the longitudinal plate portions 72 of two leaf springs having a square bracket shape. Each of the second backing plates 79 is preferably provided by a metal plate having a cross section of, e.g., substantially square bracket shape, and is provided with through-holes (not shown) arranged to permit insertion of the second bolts 78. The second bolts 78 are inserted into the through-holes of the second backing plates 79 and the through-holes of the roller holders 40B and are threadedly coupled with the second nuts 80.

The second nuts 80 are preferably provided by, e.g., rectangular metal plates, and are provided with female threads threadedly coupled with the second bolts 78. Use of the second bolts 78, the second backing plates 79 and the second nuts 80 makes it possible to firmly fix the longitudinal plate portions 72 to the roller holders 40B with the surface pressures of the second backing plates 79 and the second nuts 80.

As can be seen in FIGS. 10 and 11, the reception groove portions 77 are grooves defined in the rotor body 20B to extend in the extension direction P1 of the driving shaft 4 a and opened in a substantially T-like shape. The reception groove portions 77 communicate with the through-holes set forth above. As shown in FIG. 11, the first nuts 75 are arranged within the reception groove portions 77. Use of the reception groove portions 77 makes it possible to accommodate the first nuts 75 and the tip end portions of the first bolts 73 within the rotor body 20B. Accordingly, it is possible to reduce the dimension of the rotor body 20B in the insertion direction of the first bolts 73.

The stopper portions 82 are defined in the rotor body 20B to extend in the extension direction P1 of the driving shaft 4 a and to protrude toward the roller holders 40B. The stopper portions 82 restrict the amount of bending of the longitudinal plate portions 72 toward the rotor body 20B, thereby preventing excessive bending of the longitudinal plate portions 72 and occurrence of metal fatigue in the leaf spring 70.

Next, the operation of the tube pump 1B of the third preferred embodiment will be described with reference to FIG. 13. FIG. 13 is a plan view illustrating the operating state of the rotor unit 5B of the tube pump 1B. If the rotor body 20B is rotated, e.g., counterclockwise, by the rotation of the driving shaft 4 a as illustrated in FIG. 13, the pressing roller 50 biased by the leaf spring 70 (mainly by the longitudinal plate portions 72) (namely, the pressing roller 50 positioned at the upper side in FIG. 13) presses the tube 3. At this time, the pressing roller 50 receives a reaction force (load) from the tube 3. The load acts against the roller holder 40B supporting the pressing roller 50 (namely, the roller holder 40B positioned at the upper side in FIG. 13).

The roller holder 40B swings (gets tilted) clockwise with respect to the rotor body 20B while bending the leaf spring 70 (mainly the transverse plate portions 71) to release the load. This reduces the load applied to the roller holder 40B, thereby preventing the load from being applied to the rotor body 20B through the roller holder 40B. As a result, it is possible to prevent an occurrence of large torque variation in the driving shaft 4 a.

If the rotor body 20B further rotates and if the pressing roller 50 pressing the tube 3 becomes detached from the tube 3 and fails to receive the load from the tube 3, the roller holder 40B is returned to the pre-swing position by the biasing force (restoring force) of the leaf spring 70 (mainly the transverse plate portions 71). By such rotation of the rotor body 20B, the other pressing roller 50 kept out of contact with the tube 3 (the pressing roller 50 positioned at the lower side in FIG. 13) operates just like the pressing roller 50 positioned at the upper side in FIG. 13. As the rotor body 20B rotates in this manner, the tube 3 is continuously squeezed by the pressing rollers 50 to discharge the liquid existing therein.

On the other hand, if the rotor body 20B is rotated in the reverse direction, the same operation as stated above occurs except that the roller holders 40B swing in the direction opposite to the afore-mentioned direction (clockwise). The same actions occur as in the counterclockwise rotation. Regardless of whether the rotor body 20B is rotated in the forward direction or in the reverse direction, it is therefore possible to drive the drive motor 4 with no occurrence of large torque variation in the drive motor 4.

The tube pump 1B of the third preferred embodiment described above provides the same effects as those of the first preferred embodiment and additionally provides the following effects. The tube pump 1B of the third preferred embodiment includes the leaf spring 70 preferably having a substantially polygonal sleeve shape defined by the transverse plate portions fixed to the rotor body 20B and the longitudinal plate portions 72 fixed to the roller holders 40B. Use of the leaf spring 70 makes it possible to simplify the configuration of the biasing unit. By fixing the transverse plate portions 71 of the leaf spring 70 to the rotor body 20B, it is possible to sufficiently secure the bending amount of the leaf spring 70 and to reduce the thickness of the leaf spring 70.

Fourth Preferred Embodiment

Next, a tube pump 1C according to a fourth preferred embodiment of the present invention will be described with reference to FIGS. 14 through 17. FIG. 14 is a perspective view showing a rotor unit 5C of a tube pump 1C. FIG. 15 is a section view of the rotor unit 5C taken along line XV-XV in FIG. 14. FIG. 16 is a section view of the rotor unit 5C taken along line XVI-XVI in FIG. 14. FIG. 17 is a plan view illustrating the operating state of the rotor unit 5C.

The tube pump 1C of the fourth preferred embodiment preferably includes a casing 2, a tube 3 and a rotor unit 5C arranged to squeeze the tube 3 upon rotation of a driving shaft 4 a (see FIG. 17). As shown in FIGS. 14 through 16, the rotor unit 5C preferably includes a pair of biasing portions (biasing units) 90, a rotor body 20C, a pair of roller holders 40C and a pair of pressing rollers 50 rotatably supported on the roller holders 40C.

As can be seen in FIGS. 14 and 15, each of the biasing portions 90 preferably has a bellows shape defined by a resin plate having specified predetermined elasticity. The biasing portions 90 are configured to expand and contract in the biasing direction P2 (FIG. 15).

The rotor body 20C is preferably made of the resin material stated above and preferably has a substantially elliptical columnar shape. The biasing portions 90 are arranged at the opposite sides of the rotor body 20C such that the biasing direction (the expansion-contraction direction) P2 (or P3) thereof extends parallel or substantially parallel to the major axis of the rotor body 20C. The rotor body 20C is integrally fixed to the biasing portions 90 at the base sections 90 a of the biasing portions 90 in the biasing direction P2.

The roller holders 40C are preferably made of the resin material described above and preferably have a substantially triangular columnar shape, for example. The roller holders 40C are integrally fixed to the biasing portions 90 at the opposite end sections 90 b of the biasing portions 90 in the biasing direction P2. The biasing portions 90, the rotor body 20C and the roller holders 40C are preferably molded into a single piece, for example.

Next, the operation of the tube pump 1C of the fourth preferred embodiment will be described with reference to FIG. 17. FIG. 17 is a plan view illustrating the operating state of the rotor unit 5C of the tube pump 1C. If the rotor body 20C is rotated, e.g., counterclockwise, by the rotation of the driving shaft 4 a, the pressing roller 50 biased by the biasing portions (namely, the pressing roller 50 positioned at the upper side in FIG. 17) presses the tube 3. At this time, the pressing roller 50 receives a reaction force (load) from the tube 3. The load acts against the roller holder 40C supporting the pressing roller 50 (namely, the roller holder 40C positioned at the upper side in FIG. 17).

The roller holder 40C swings (becomes tilted) clockwise with respect to the rotor body 20C while bending the biasing portions 90 to release the load. This reduces the load applied to the roller holder 40C, thereby preventing the load from being applied to the rotor body 20C through the roller holder 40C and the biasing portions 90. As a result, it becomes possible to prevent an occurrence of large torque variation in the driving shaft 4 a.

If the rotor body 20C further rotates and if the pressing roller 50 pressing the tube 3 becomes detached from the tube 3 and fails to receive the load from the tube 3, the roller holder 40C will be returned to the pre-swing position by the biasing force (restoring force) of the biasing portions 90. By such rotation of the rotor body 20C, the other pressing roller 50 kept out of contact with the tube 3 (the pressing roller 50 positioned at the lower side in FIG. 17) operates just like the pressing roller 50 positioned at the upper side in FIG. 17. As the rotor body 20C rotates in this manner, the tube 3 is continuously squeezed by the pressing rollers 50 to discharge the liquid provided therein.

On the other hand, if the rotor body 20C is rotated in the reverse direction, the same operation as described above occurs except that the roller holders 40C swing in the direction opposite to the afore-mentioned direction (clockwise). The same actions occur as in the counterclockwise rotation. Regardless of whether the rotor body 20C is rotated in the forward direction or in the reverse direction, it is therefore possible to drive the drive motor 4 with no occurrence of large torque variation in the drive motor 4.

The tube pump 1C of the fourth preferred embodiment described above provides the same effects as those of the first preferred embodiment and additionally provides the following effects. In the tube pump 1C of the fourth preferred embodiment, each of the biasing portions 90 is formed into a bellows shape by a resin plate having a specified predetermined elasticity and is configured to flex back and forth to allow swinging of the pressing rollers 50 in the direction perpendicular or substantially perpendicular to the biasing direction. The rotor body 20C is preferably made of a resin and is integrally fixed to the biasing portions 90 at the base sections 90a of the biasing portions 90 in the biasing direction P2. The roller holders 40C are preferably made of a resin and are integrally fixed to the biasing portions 90 at the opposite end sections 90 b of the biasing portions 90 in the biasing direction P2. Accordingly, the rotor body 20C, the biasing portions 90 and the roller holders 40C can be molded into a single monolithic piece by the resin mentioned above.

While certain preferred embodiments of the present invention have been described above, the present invention is not limited to the foregoing preferred embodiments but may be modified and/or combined as desired.

For example, while each of the rotor body 20 and the roller holders 40 is preferably provided by a single piece of an engineering plastic in the first to third preferred embodiments, the present invention is not limited thereto. For example, only the rotor body 20 may be provided by a single piece of an engineering plastic. The rotor body 20 and the roller holders 40 or the rotor body 20 may be provided by a single piece of a resin other than an engineering plastic, as far as the resin complies with the prescribed requirements on, e.g., heat resistance, strength, flexural modulus, etc.

While two pressing rollers 50 are preferably provided along the biasing direction P2 in the rotor unit 5, 5A, 5B, or 5C in the first to fourth preferred embodiments, the present invention is not limited thereto. For instance, three or more pressing rollers 50 may be provided in the rotor unit 5, 5A, 5B, or 5C. The number of the tube guide rollers 47 may also be increased if necessary.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims. 

1. A tube pump, comprising: a casing including an arc-shaped inner circumferential wall surface along which a liquid-flowing tube is arranged; a drive motor provided with a driving shaft rotatable in forward and reverse directions; a rotor body arranged in a center position of the arc-shaped inner circumferential wall surface to rotate together with the driving shaft; roller holders supported on the rotor body to swing with respect to the rotor body and arranged to move both toward and away from the driving shaft on a plane that is perpendicular or substantially perpendicular to the driving shaft; pressing rollers rotatably supported on the roller holders to press the tube against the inner circumferential wall surface; and biasing units interposed between the rotor body and the roller holders to bias the roller holders away from the driving shaft and to bias the roller holders, when swung, to be returned to a pre-swing position, the roller holders being configured to swing with respect to the rotor body in a direction opposite to a rotation direction of the rotor body.
 2. The tube pump of claim 1, wherein the rotor body includes engagement projection portions extending in an extension direction of the driving shaft and engaging with the roller holders, the engagement projection portions being arranged in opposite side areas of the rotor body along a direction that is perpendicular or substantially perpendicular to the extension direction of the driving shaft and the biasing direction of the biasing units, each of the engagement projection portions including a metal shaft portion fixed to the rotor body and a resin or metal collar portion rotatably supported on the shaft portion, each of the roller holders including an engagement recess portion extending in the extension direction of the driving shaft and engaging with the collar portion.
 3. The tube pump of claim 1, wherein the rotor body includes engagement projection portions extending in an extension direction of the driving shaft and slidably engaging with the roller holders, the engagement projection portions arranged in opposite side areas of the rotor body along the direction that is perpendicular or substantially perpendicular to the extension direction of the driving shaft and the biasing direction of the biasing units, the roller holders including engagement recess portions extending in the extension direction of the driving shaft and slidably engaging with the engagement projection portions.
 4. The tube pump of claim 1, wherein the biasing units includes a leaf spring defined by a substantial sleeve-shaped configuration including a pair of transverse plate portions extending parallel or substantially parallel to a biasing direction of the biasing units and a pair of longitudinal plate portions extending in a direction perpendicular or substantially perpendicular to the transverse plate portions to interconnect opposite end sections of the transverse plate portions, the transverse plate portions fixed to the rotor body, the longitudinal plate portions fixed to the roller holders.
 5. The tube pump of claim 1, wherein the biasing units have a bellows configuration defined by resin plates having a predetermined elasticity to expand and contract in a biasing direction, the rotor body being made of the resin and integrally fixed to the biasing units at base sections of the biasing units, the roller holders being made of the resin and integrally fixed to the biasing units at end sections of the biasing units in the biasing direction.
 6. A tube pump, comprising: a casing including an arc-shaped inner circumferential wall surface along which a liquid-flowing tube is arranged; a drive motor provided with a driving shaft rotatable in forward and reverse directions; a rotor body arranged in a center position of the arc-shaped inner circumferential wall surface to rotate together with the driving shaft; roller holders engaging with the rotor body to move both toward and away from the driving shaft on a plane perpendicular or substantially perpendicular to the driving shaft and swingably engaging with the rotor body; pressing rollers rotatably supported on the roller holders to press the tube against the inner circumferential wall surface; and biasing units arranged between the rotor body and the roller holders to bias the roller holders away from the driving shaft and to bias the roller holders, when swung, to be returned to a pre-swing position, the rotor body including a pair of engagement projection portions extending in an extension direction of the driving shaft, the engagement projection portions being arranged in opposite side areas of the rotor body along a direction that is perpendicular or substantially perpendicular to the extension direction of the driving shaft and the biasing direction of the biasing units, the roller holders including a pair of engagement recess portions extending in the extension direction of the driving shaft and engaging with the engagement projection portions to define rotation fulcrums of the roller holders.
 7. The tube pump of claim 6, wherein the rotor body is made of resin or the rotor body and the roller holders are made of resin.
 8. The tube pump of claim 6, wherein each of the engagement projection portions includes a metal shaft portion fixed to the rotor body and a resin collar portion covering the shaft portion.
 9. The tube pump of claim 6, wherein the engagement projection portions are defined by a single monolithic piece with the rotor body.
 10. The tube pump of claim 6, wherein the biasing units include compression coil springs, the rotor body including spring-receiving recess portions recessed toward the driving shaft and arranged to accommodate the compression coil springs. 